Injector for molding machines



July 19, 1949. c. Jo s'r INJECTOR FOR MOLDING MACHINE Filed March 2, 1945 WEE gwue/wfo'z CONRAD rioBsz' Patented July 19, 1949 UNITED TAT-Es PATENT, OFFICE Conrad Jobst, Toledo, Ohio, assignor, by mesne assignments, to-Owens-Illinois Glass Company,

Toledo, Ohio, a corporation of Ohio I Application March 2, 1945, Serial No. 580,636

, 2 Claims. 1 My invention relates to the type in which molding material is heated and introduced into the molds through an injector or nozzle. The invention is well adapted to be embodied in machines for molding thermoplastic.-

materials which are supplied to the machine in powdered r granular form and are heated and brought to a molten or plastic conditionwhile passing through the injector tothe mold, into which the molten material is forced under high pressure.

In machines of this type, difficulty has been experienced on the account of portions of the molding material lodging in cracks, crevices, pockets or other recesses, in ,the' walls of the injector channel or passageway through which the material is conducted to the mold. When such particles or small portions become lodged in the injector and held for an undue length of time within the heated passageway, they become overheated and discolored .so that when dislodged and carried into the molds, they contaminate the molding, material and'cause. discoloration and defects in the molded articles.

An object of the present invention is to Provide an injector in which the channel for the molding material is fully streamlined in a manner to provide a smooth flow of the material and in which the channel is free from .cracks,- crevices, or joints in which portions of the material can become lodged. The invention provides a construction free from threaded connections or joints which would permit leakage of the molten molding material under the high pressure which is used, particularly as such joints tend to become loose when subjected to combined high temperatures and pressures and frequent variations in the temperatures and pressures throughout wide ranges.

A further object of the invention is to provide a novel injector providing an annular passageway through which the molding compound is conducted in a comparatively thin layer and with suitable heating means positioned both external ly and internally of said passageway in a manner to cause thorough heat soaking or uniform heating of the entire mass of the material.

Other objects of the invention will appear hereinafter.

Referring to the accompanying drawings:

Fig. 1 is a fragmentary sectional elevation of an injection molding machine/showing the dies and the injector.

Fig. 2 is a cross section of the injector and molding machines of the tip Il J 2 heater at the-line 2+2 on Fig." 1, with partsbrokenaway. I

Referring to Fig. l; themachine comprises a stationary frame including an abutment plate III, a stationary die plate or mold section. I l and a movable die plate or mold section l-2 mounted on acarriage l3. The carriage is reciprocated horizontally and moves the die plate 1i! to and from the-plate ,II for closing and opening the mold. The die plate H is attached to a'face plate l4 bolted to the abutment plate l0.

An injector l5, herein referred to as an'injection nozzle, extends forwardly through an opening in the plate It and is provided at its forward end with a tip l1 extending through'the faceplate I l and abutting the stationary die plate l l. The injection nozzle comprises a cylindrical core I1 surrounded by an exterior tubular member H3 or shell, spaced from the core to provide an annular passageway i9 through which the molding material is conducted. A tubular injection plunger is periodically. reciprocated within the passageway IQ for forcing charges of the moldingcompound into the mold.

The forward end portion 2| of the core I1 is tapered to a point. The forward portion of the shell l8-is also tapered so that the passageway 19 is forwardly convergent and merges into the cylindrical bore or passageway extending through Said bore provides a valve chamber in which a valve 22 is mounted. The valve is held open while the die plates are together by a rod 23 which is attached to the movable die plate l2 and extends through the sprue hole in the die plate H and the tip Il and into the forward end of the valve chamber.

Surrounding the shell I8 is a heater 25 in which are embedded groups of electrical heating elements 26, 2? and 28, each group being arranged in an annular series surrounding the shell Hi. The core l'l also has mounted therein an annular series of electrical heating elements 29. The passageway Hi serves as a heating chamber in which the molding material is heated and reduced to a plastic or fluid condition. The arrangement of the heating elements, both internally and externally of the annular heating chamber, permits the material to be quickly and uniformly heated throughout the mass. The heat soaking of the material insures a uniform temperature and homogeneous condition of the material as it enters the mold.

The core Il may be tubular or formed with a central bore (Fig. 2). Spacing ribs 3| formed integral with the core I1 extend lengthwise there- 3 of and each has its ends 32 tapered to a point. These ribs are arranged in parallel and spaced at equal intervals throughout the circumference of the core in an annular series. The outer faces of the ribs bear against the inner surface of the shell- I8 and are embedded therein so that the core and shell form a unitary integrated structure free fromcracks or crevices at their-uniting surfaces. The ribs with their tapered ends provide streamlined passageways therebetween, free from any corners, cracks or crevices in which the molding material could become, lodged,

The shell l8 and core I! are preferably made of the same metal, such as steel; and the shell is shrunk onto the core by assembling the parts while the shell is at a high temperature'and the core chilled to a low temperatnre -r For; this-pull:

pose the shell is heated to about an annealing temperature, approximately 550 degrees F.,whilethe core I! is chilled to about 90 degrees F. belowt zeroi While. the parts are at these temperatures, the core is dropped into the outer: shell t8; or the shell dropped onto the core- This immediately causes a rapid heat transfer from the shell-tothe core so that the shell quickly cools and-contracts while the'core expands asits temperature rises, until the temperatures are equalized; Thisresultsfin an extremel tightfit and interlocking of the parts to form practically an integral structure. This shrinking ofthe shell on the core causes the ribs to be embedded several-,thousandths of an inch Within the inner surface of theshell. Owing to this method of assembling the parts, a perfectly tight fit is maintained under, working conditions which involve high temperatures and frequent temperature changes throughout a rather-wide range.

Modifications may be resorted to within the spirit andscope of my invention.

I claim:

l. An injector for injection molding machines comprising a cylindrical core and a cylindrical shell surrounding and concentric with the core, with an annular space between the shell and core, an. annular series ofribs integralwith the core. and extending lengthwise thereof on the exterior surface of. the core, each rib having its side parallel throughout a major portion of its length, said ribs being. parallel and spaced at regular intervals around the core the ribs being of a depth to bridge the said annular space and divide it into parallel channels, the outer faces of the ribs being embedded in the inner surface of the shell and the end portions of the ribs 5 being tapered to points for streamlining the channels.

2. An injector for a molding machine, said inject r omprisin a crlin ricalic re-havin its forward endtapered to the form of a cone, a tubular shell comprising a body portion concentrio with and surrounding the core, the interior surface either said body portion being of greater diameter than th exterior surface of the core, twprovideran annular space for the passage of moldingi material the shell including a forward end 'por tion integral with and forming an extension of saidbody portion, said end portion surrounding said cone and being tapered concentrical-ly with said cone and forming therewith a convergent extension of said annular passagewarl-thewallthickness of; th ellbeing su stantiallr mie rnuehoutt length e e f, h atinesm anssurround g the s body po (1 tiered-end portion of the shell, said core teg'ralribs, on its exterior surface exr gthwizsethereofand bridging the said annulan 13 33; said shell and cor Consistin of me 1., heshell beingr nk onto the core with the r embe de in the nte or. sur o he vS.h'l -i,

CONRAD JOBST;

REFERENCES CITED The following references-are of record in the file of thispatent:

, UNITED STATES. PATENTS Number Name 

